Signals of multiple bands may be transmitted and received in wireless communication devices such as mobile phone terminals. For example, LTE (Long Term Evolution) or the like uses bands including a low band of 1 GHz or lower, a middle band around 2 GHz, and a high band around 2.5 GHz. Each of the low band, the middle band, and the high band includes two or more bands each including a transmit band and a receive band.
Sharing an antenna terminal between the low band and the middle band with use of a diplexer is disclosed in Japanese Patent Application Publication No. 2014-526847 (Patent Document 1), U.S. Patent Application Publication No. 2006/0128393 (Patent Document 2), and International Publication No. 2012/093539 (Patent Document 3). Patent Document 2 discloses an art that uses individual antenna terminals for the low band, the middle band, and the high band. Patent Document 3 discloses an arrangement of filters for two or more bands.
When separate antenna terminals are provided as described in Patent Documents 1, 2, the interference between the bands is reduced (for example, the isolation is improved), but three connectors for RF (Radio Frequency) are required, and thus the cost and the size increase. On the other hand, when the antenna terminal is shared, the cost and the size can be reduced, but the interference between the bands increases. For example, when three antenna terminals are unified to be a shared single antenna, the number of required RF connectors becomes one, but the loss of a multiplexer and/or the interference between the bands increases. Moreover, the methods disclosed in Patent Documents 1 through 3 fail to sufficiently reduce the interference between the bands.